The commercial shipping industry relies upon proper handling of cargo containers. Containers known as Unit Load Devices (“ULDs”) commonly are used to load cargo onto aircraft. ULDs are containers and platforms of various sizes and shapes, including box-like enclosures, pallets, and the like. ULDs are sized and shaped such that they can be compactly loaded together in an aircraft cargo compartment. ULDs are loaded onto aircraft and unloaded from aircraft using various types of automatic loading equipment in order to minimize loading and unloading time. Aircraft cargo holds often are provided with ball transfer units and rollers to facilitate movement of ULDs in the cargo hold as the ULDs are loaded and unloaded. In addition, various types of restraint mechanisms are used for restraining stowed ULDs within cargo holds during transit. For example, various types of restraint devices commonly are used to inhibit lateral, longitudinal and/or vertical movement of stowed ULDs.
Longitudinal, lateral and vertical restraint devices can be installed within the cargo system trays, or can be mounted directly to an aircraft structure for use in restraining stowed ULDs during transit. Often such restraint devices are configured to be recessed below the conveyor plane (generally coinciding with the bottom surfaces of the ULDs) when not in use, and to be selectively raised for engagement with loaded ULDs once the ULDs are in their stowed positions. At the forward and aft ends of a cargo compartment, fixed end stops commonly are used to at least partially restrain the forward-most and aft-most ULDs within the cargo compartment. In addition, restraints and end stops can be installed between containers and pallets when both containers and pallets are transported together.
ULDs are designed such that they compactly fit within a plurality of rows or lanes within an aircraft's cargo hold. Normally, the lanes are arranged such that only small gaps exist between ULDs in adjacent container lanes, thereby effectively maximizing the use of the available storage volume. ULDs are loaded onto an aircraft through aircraft cargo doors, and can be loaded in a predetermined order by cargo-loading lanes. The last ULDs loaded onto an aircraft must be inserted into a final cargo-loading lane that lies between ULDs previously loaded in adjacent container lanes or between a previously loaded ULD and an end stop.
Because a cargo-loading lane can be only slightly wider than a ULD it receives, inserting a ULD into a final cargo-loading lane between previously loaded container lanes or end stops (sometimes referred to as “threading the needle”) can be difficult. Misalignment between a ULD and a final cargo-loading lane as the ULD is delivered through a doorway by automated loading equipment can cause the ULD to jam, possibly resulting in substantial delays and equipment damage. Large lateral guides are known for guiding ULDs through a doorway and into a final container lane. These large lateral guides extend across the doorway and act to funnel the ULDs toward the center of the doorway and toward the center of a final container lane. Often, however, such large lateral guides are unavailable, or cannot be installed on a particular aircraft or during a particular loading event. In such cases, a standard cargo restraint is used as a lateral guide for the final cargo container lane and is relied upon to center a ULD within the loading lane. Unfortunately, ULDs can impact and hang up on such restraints, sometimes resulting in damage to the impacted restraints and/or ULDs and delaying loading of the impeded ULDs.
Accordingly, there is a need for a new lead-in device and method for facilitating the loading of ULDs into a narrow cargo container lane. In particular, there is a need for a ULD lead-in device that is substantially more compact and is quicker and easier to install and operate than known large lateral guides. Preferably, the device and method should be compatible with known ULD loading and restraint equipment. In addition, the device and method should be adaptable to the cargo-loading lane bounded by adjacent ULDs and end stops, which can vary in their positions on either side of the cargo-loading lane.